This invention concerns electrically operated parking brakes, in which an electric motor is selectively energized as by depressing a switch to operate the parking brake so as to be released or engaged.
U.S. Pat. No. 6,386,338 assigned to the same assignee as the present application describes an arrangement for electrically operating a parking brake, with an alternative manual operator and that patent is incorporated herein by reference.
In the alternative manual operation, one end of an inner core of a flexible Bowden type cable is engaged with a hand tool to enable the cable to be rotated, causing a spur gear connected to the other end of the core, which in turn drives gearing connected to a screw shaft, able to also be driven by an electric-motor. This causes advance of a nut on the screw shaft. A second flexible cable core is attached at one end to the nut and at the other end to the parking brake, to either set or release the brake by rotation of the screw shaft in respective directions, either manually as described or by selective energization of the electric motor. In order to avoid rotation of the flexible cable core that is used to manually operate the brake during electric operation, an arrangement is provided to mechanically uncouple the flex cable core from the gear used to drive the screw shaft except when a tool is operatively engaged with the other end of the flexible cable core. This arrangement is mechanically complex and requires an additional effort by the person manually operating the parking brake.
It is the object of the present invention to provide a simplified arrangement and method for uncoupling an alternative manual operator for an electrically operated parking brake which does not entail an extra effort by the user when the parking brake is operated manually.
The above recited object and other objects of the invention which will become apparent upon a reading of the following specification and claims are achieved by providing a slidable coupling which is spring urged to drivingly connect one end of a flex cable core with a gear engaged with the parking brake gearing normally driven by an electrical motor. The flex cable extends to a tool drive fitting located on the vehicle to be conveniently accessible for manual operation of the parking brake. A solenoid causes shifting of the coupling so as to disconnect the flex cable core from the associated gear whenever the electric motor is energized so that the flex cable is not driven when the parking brake is being electrically operated.